1. Field of the Invention
The present invention relates to a liquid crystal display device and driving method thereof, and more particularly to a liquid crystal display device which enables double-sided indication, and the driving method thereof.
2. Description of the Related Art
The liquid crystal display device is a display device having advantageous features, such as low power consumption, thin shape and light weight. Their utilization scenes are more and more increased. The manufacturing technology is established with required screen sizes, large-sized electronic equipment such as a large-screen TV, medium-sized electronic equipment such as a notebook personal computer and a display monitor, and small-sized electronic equipment such as a portable telephone and PDA, and it is put in practical use in various screen sizes.
Generally the liquid crystal display device includes: a liquid crystal panel, a drive control circuit for controlling the display image of the liquid crystal panel, a terminal part that consists of operation keys for adjusting the displaying condition of the liquid crystal panel, and the power supplying part which supplies operation power to these element. With the liquid crystal display device, the single-sided indication as which a user regards the image displayed on the liquid crystal panel of one sheet from one side has so far been used mainly. However, in order to increase the amount of displayed information, the double-sided indication device is proposed by arranging two liquid crystal panels back to back.
Moreover, a further advanced double-sided indication device is proposed by using a single liquid crystal panel. For example, the single liquid crystal panel has an upper area and a lower area so as to be considered as a front-side display area and a rear-side display area, respectively. Such a double-sided display is proposed by Japanese Laid-Open Patent No. 2001-312228, wherein a liquid crystal panel is incorporated into a foldaway cellular phone. The upper area is used as an inner side indication area, and the lower area is used as an outside indication area. When an user opens or unfolds the cellular phone, the user can see the indication on the inner side indication area. When the user closes or folds the cellular phone, the user can see the indication on the outside indication area.
In Japanese Laid-Open Patent No. 2003-35893, another double-sided indication device with a single liquid crystal panel is proposed. Here, light guide plates, back light units, and dimming glasses are arranged in front of and rear of single liquid crystal panel, respectively. These are incorporated in a lid of a foldable portable information device. When the lid is lifted, a back light located outside of the lid is turned on, and a rear dimming glass located outside of the lid is made into an opaque state, and a front dimming glass located inside the lid is made into a transparent state. Thereby, a user can seethe indication on the inner side indication area. When the lid is folded, a back light located inside the lid is turned on, the front dimming glass is made into an opaque state, and the rear dimming glass located is made into a transparent state. Thereby, a user can see the indication on the outside indication area.
However, in the liquid crystal display device proposed by the above-stated Japanese Laid-Open Patent No. 2001-312228, since the double-sided indication is realized by dividing a liquid crystal panel into two areas, the whole display area is the same as the case of a single-sided display. Thus, the problem occurs that the spatial relationship of an inner side indication area and an outside indication area is fixed, and the flexibility which arranges a display area becomes small.
In the above-stated Japanese Laid-Open Patent No. 2003-35893, on the other hand, since the double-sided display is realized by arranging a light guide plate and the back light at front and rear sides of a liquid crystal panel, respectively, the foregoing problem does not occur. However, it cannot simultaneously display on the both sides of a liquid crystal panel.